The long term objective of this proposal is to establish the physical map and characterize the molecular structure of the region surrounding the Ph, Rw and W loci on mouse chromosome 5. These three genes are located within 3 cM and are defined by dominant mutations that have similar effects on pigmentation and development. Alleles of two mutations (W, Ph) are associated with mutations/deletions of genes encoding growth factor receptors. Based on the way the third mutation, Rw, was generated it is likely that this mutation also represents a deletion. Chromosome walking using yeast artificial chromosome (YAC) and jumping libraries will be used to isolate overlapping sets of genomic clones (contigs) around available molecular probes. In order to determine the order, physical distance and overlap between contigs, their end clones will be mapped genetically and by pulsed field gel electrophoresis (PFGE). The PFGE analysis of end clones in W19H, Ph-and Rw DNA will facilitate physical mapping, and will also allow us to identify the breakpoints and determine the size of the chromosomal aberrations associated with theW19H, Ph and Rw mutations. A physical map of the region around Ph, Rw and W will contribute to our understanding of the chromosomal organization around these phenotypically related, developmentally interesting genes. In addition this study win provide a model of a combined genetic and molecular analysis of a delimited region of the mouse genome and will provide useful gene-probes for the homologous region on human chromosome 4.